Research On Influence Mechanism Of Relay Protection In Electric Power Networks Caused By Access Of Small Hydropower Stations

Small hydropower stations accession not only results in higher reliable power supply in the user side, but their high penetration of large-scale distributed make efficient cascade utilization of all kinds of energy. Nonetheless, it is their flexible access locations as well as volatile and intermittent power supply that lead to power flows tow-way within the network, meaning that the traditional distribution network protection based on single-ended electrical signal has no longer suitable for fault diagnosis and start in this double-ended power flow situation. In terms of size and nature, meanwhile, the fault current would be changed largely result from Small hydropower stations’ accession. This means that the reliability, selectivity, sensitivity and speed continuity of traditional distributed network protection cannot fully meet the requirements of this new operation standard, and accordingly its protection technology has become one of the bottlenecks to cultivate this renewable resource. Thus, this thesis mainly studies on Influence Mechanism of Relay Protection in Electric Power Networks Caused by Access of Small Hydropower Stations through Simulation calculation and research in PSCAD/EMTDC environment, with the aim of overcoming the malpractice of traditional distribution network protection and meeting this new technical environment.First, according to structure and operation characteristics of the small hydropower and the accession diagram in South China, studies the principle and composition of various modules in this new distribution network。On this basis, builds corresponding small hydropower stations, distribution network and protection module in PSCAD/EMTDC environment, and then combines them together to construct the distribution network with relative essential components.Moreover, there is a study on the potential impact of three-set current protection I and II in a typical IEEE7 distribution network accessed small hydropower stations, from both theory and simulation aspects. After that, it analyzes the maximum capacity into the Power Grid of the hydropower on the condition that the three-set current protection can be reliable.Additionally, the following research on what actual effects it will have on the Inverse time over current protection when the Small hydropower stations accession by means of steady and transient simulation. More specifically, main emphasis of this research is the possible impact on the reliability of this protection strategy in various capacity of the hydropower, stem from which summarizes those requirements and conditions for the reliable operation of this protection in network with the Small hydropower stations accession.Finally, the distance protection module is constructed in PSCAD/EMTDC environment. Following this, Start with both access capacity and position, it analysis those possible effects it would have on the distance protection I and II section. Thus, what the rule of reliable application of distance protection can be obtained from those simulation results in this new engineering environment.